Conventionally, imaging devices such as endoscopes for imaging the inside of pipes and the like are known (for example, Patent Literature 1). For example, the endoscope has an imaging unit at a tip end portion of a cable to be inserted into pipes and the like. Upon operating an operation unit by a user, the tip end portion of the cable is directed at a desired direction, so that the imaging direction of the imaging unit is changed to the desired direction. Images captured by the endoscope are displayed on a display unit.
An object can be seen in an image captured by the imaging device, but the size of the object is difficult to recognize. For example, since the distance between the imaging unit and the object changes in accordance with an insertion state and the imaging direction of the cable, the size of the object is difficult to grasp from the captured image. Furthermore, the imaging device changes the size of the imaged object in the captured image by zooming in or out the object by an imaging optical system, and therefore the size of the object is difficult to grasp from the captured image.